This invention relates to a synthetic shaped article and its method of preparation. Particularly, this invention relates to a synthetic shaped article which simulates marble, granite or the like, and its method of preparation.
Simulated marble, granite or other simulated stone surfaces have become a popular building material. Articles made from these materials include architectural facings, exterior and internal wall panels, light fixtures, bathroom fixtures, counter tops, table tops, floors and other articles for which real stone is used. As compared to natural marble or granite, simulated marble or granite is less expensive, lighter, not as easily chipped, and has a greater uniformity of particle size, type and color.
Various techniques for forming simulated marble or granite are known. For example, U.S. Pat. No. 3,341,396 to Iverson proposes an "outmold" casting technique comprising applying a pigmented coating of a thermosetting resin to a substrate (e.g., wood, brick, etc.), followed by applying a base layer having a color pigment, and then applying a transparent coating layer on top of the color pigmented base layer. U.S. Pat. Nos. 4,433,070 and 4,544,584 to Ross et al propose "inmold" casting techniques comprising forming a cultured marble or like mineral appearance surface by introducing a first resin hardened to a predetermined hardness and distributing it in a second liquid resin. U.S. Pat. No. 4,959,401 to Bellasalma et al proposes another inmold casting technique using a thermoset portion and an inorganic particulate portion of naturally occurring minerals.
These prior techniques for forming simulated stone have several disadvantages. If inorganic particles are used, the simulated stone often has weak areas at the boundaries where the inorganic particles and the resin contact each other. This results in a susceptibility to uneven cracking along the contours of the inorganic particles. This limits the ability to widely use the article particularly when the article is susceptible to being cracked from exertion of external forces. Moreover, the ability to create different and aesthetically pleasing patterns using these techniques is also limited.
A solution to the aesthetic problem is proposed in U.S. Pat. No. 4,818,570 and U.K. Patent No. 2,151,906 both to Milles. These patents propose forming an amorphous simulated stone-like material by mixing a resin, an inorganic filler and pigment to form a paste having a high viscosity which is cut into pieces, coated with additional pigment to create the desired aesthetic effect, and recombined under pressure. The resulting stone-like material, however, may have weak areas at the boundaries where the resin and filler and resin and pigment are in contact with each other.
Accordingly, it would be desirable to provide a method of producing a synthetic shaped article simulating marble, granite or the like which is strong, is relatively free of weak areas, and permits the production of different and aesthetically pleasing patterns.